Various drying compositions are known in the prior art. These compositions contain various kinds and various amounts of surfactants and other additives. Specifically, the concentration of surfactants added to chlorocarbon and chlorofluorocarbon solvents, such as, methylene chloride and 1,1,2-trichloro-1,2,2-trifluoroethane typically are in amounts of 500 ppm or greater.
Such relatively large quantities of surfactant are a drawback in the elimination of residues, of which the cleaned surface must be free, for various applications such as in the semiconductor field.
Another drawback in various compositions that have been utilized in the prior art is attributable to the changing composition of the water displacement composition as the composition absorbs, or is depleted of a portion of ingredients. With respect to amounts of surfactant, a decreased surfactant level provides for shortened process time in that less non-volatile material (surfactant) is carried from the drying and displacing sump of a surfactant dryer to the rinse sump and hence requires a shorter rinse time to wash off the surfactant that was carried over.
The use of an azeotropic mixture improves solvent wettability in the liquid and vapor zones of a typical solvent dryer. Though the lifetime of the enhanced wettability can be affected by the susceptibility of the azeotropic mixture to water, the composition should be less affected by water than such components known in the prior art (U.S. Pat. Nos. 3,559,297; 3,589,023; and 3,710,450) and provide enhanced wettability over a longer lifetime. Improvement of conservation of desirable phase separation rates, with no emulsion formation, over a pH range of 4 to 11 is also an important consideration. Some systems of the prior art incorporate surfactants that can be rendered ineffective by reaction with water in extremes of pH or by reaction with metal ions to form water-extractible soaps. (U.S. Pat. Nos. 3,386,181 and 4,401,584.) Such systems typically operate where the pH of water to be removed is between 5 and 9.
It is thus apparent that a need exists for an improved water displacement composition which avoids the above drawbacks in that it results in less residue and requires less rinse time, avoids emulsion formation and is substantially more stable and resistant to composition change.